function dx = plant(t, x)
    dx = zeros(4, 1);
%***************************变量简化**************************************
x1 = x(1);  x2 = x(2);  integarl_para = x(3);   g = x(4);
%***************************系统参数**************************************
ax = -25*x1;    bx = 133;
beta0 = 1;  beta1 = 1;
k1 = 1; k2 = 1; k3 = 1; k4 = 1;
%***************************系统干扰**************************************
dt = 3*sin(2*pi*t); 
%***************************滑模面****************************************
s = x2 + integarl_para;
%***************************控制输入**************************************
u = 1/bx*( -ax - beta1*(sig(x2,2/3) + beta0 * sig(x1,1/2)) - k1*sig(s,1/2) - k2*s + g );


%***************************系统******************************************
dx(1) = x2;
dx(2) = ax + bx * u + dt;
dx(3) = beta1*( sig(x2,2/3) + beta0 * sig(x1,1/2) );
dx(4) = -k3*sign(s) - k4*s;
end


